As is well known, various glass sheets such as glass substrates for flat panel displays (FPD) including a liquid crystal display and an OLED display may be conveyed at high speed while being placed on a plurality of conveying belts that are arrayed in parallel at intervals (see, for example, Patent Literatures 1 and 2).
On a conveying path, an end-surface process such as grinding is performed on both edges of a glass sheet in a width direction that is orthogonal to a conveying direction. In this case, in order to ensure process accuracy, prior to the end-surface process, it is necessary to accurately position the glass sheet on the conveying belts. At the time of the positioning, in general, the glass sheet is moved on the conveying belts in the direction that is orthogonal to the conveying direction, and the position and the direction of the glass sheet with respect to the conveying belts are adjusted.